Wind turbine drive control device and control method of wind turbine drive device

ABSTRACT

A wind turbine drive control device according to one aspect of the present invention is a wind turbine drive control device for controlling at least one drive device for moving two structures included in a wind power generation device relative to each other, the wind turbine drive control device including: an obtaining unit for obtaining information related to a load occurring between the at least one drive device and one of the two structures that receives a force generated by the at least one drive device; and a control unit for controlling the at least one drive device so as to cause a force generated by the at least one drive device to be reduced or zero based on the information related to the load obtained by the obtaining unit during a stop period in which the two structures are stopped relative to each other.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims the benefit of priority fromJapanese Patent Application Serial No. 2019-234146 (filed on Dec. 25,2019), the contents of which are hereby incorporated by reference intheir entirety.

TECHNICAL FIELD

The present invention relates to a wind turbine drive control device anda control method of a wind turbine drive device.

BACKGROUND

Some of conventionally known wind power generation devices have a yawcontrol function for adjusting the orientation of a blade in accordancewith the wind direction. An example of such wind power generationdevices is disclosed in Japanese Patent Application Publication No.2015-140777 (“the '777 Publication”). The wind power generation devicedisclosed in the '777 Publication is installed on the land or on theocean, and it includes a tower serving as a support post for a powergenerator, a nacelle disposed on top of the tower and containing thepower generator, and a rotor disposed on one end of the nacelle andformed of a hub and a blade for converting the received wind force intorotation energy. This wind power generation device includes a yaw driveunit disposed in a connection portion between the tower and the nacelleand configured to control the positions of the nacelle and the rotorrelative to the tower. The '777 Publication discloses that the providedwind power generation device has a high availability, which is achievedby the yaw drive unit that stops transmission of a yaw drive force tominimize an impact of yaw control failure due to malfunctions of the yawdrive device.

In the above wind power generation device, when fixation occurs betweena yaw bearing gear and a pinion gear due to gear deformation caused bystrong winds such as those of a typhoon, the transmission of the yawdrive force from the pinion gear to the yaw bearing gear is stopped. Inthe above wind power generation device, the fixation between the yawbearing gear and the pinion gear is detected when the electric currentin the yaw inverter exceeds a rated current or a predetermined interlockvalue.

However, in the wind power generation device, the load between thepinion gear and the yaw bearing gear may change during the turning ofthe nacelle for adjusting the orientation of the blade, as well asduring the stop period of the nacelle in which the orientation of theblade is fixed. Such a change in the load may cause a malfunction.

SUMMARY

The present invention addresses the above drawback, and one objectthereof is to provide a wind turbine drive control device and a controlmethod of a wind turbine drive device that are capable of reducing theload occurring in the stop period.

To achieve the above object, a wind turbine drive control deviceaccording to one aspect of the present invention is a wind turbine drivecontrol device for controlling at least one drive device for moving twostructures included in a wind power generation device relative to eachother, the wind turbine drive control device comprising: an obtainingunit for obtaining information related to a load occurring between theat least one drive device and one of the two structures that receives aforce generated by the at least one drive device; and a control unit forcontrolling the at least one drive device so as to cause a forcegenerated by the at least one drive device to be reduced or zero basedon the information related to the load obtained by the obtaining unitduring a stop period in which the two structures are stopped relative toeach other. With this configuration, the load can be reduced during thestop period in accordance with the information related to the load.

In the above wind turbine drive control device, the information relatedto the load may be information based on a force acting on a fastenerfixing the at least one drive device to one of the two structures. Withthis configuration, the information related to the load can be obtainedusing the force acting on the fastener.

To achieve the above object, a wind turbine drive control deviceaccording to one aspect of the present invention is a wind turbine drivecontrol device for controlling at least one drive device for moving twostructures included in a wind power generation device relative to eachother, the wind turbine drive control device comprising: a control unitfor controlling the at least one drive device so as to cause a forcegenerated by the at least one drive device to be reduced or zero when apredetermined timing is reached during a stop period in which the twostructures are stopped relative to each other. With this configuration,the load occurring in the stop period can be reduced before the stopperiod is ended.

In the above wind turbine drive control device, the predetermined timingmay be a timing reached at regular intervals within the stop period.With this configuration, the load occurring in the stop period can bereduced at regular intervals.

In the above wind turbine drive control device, the predetermined timingmay be a timing reached a predetermined amount of time before a start ofa drive period in which the two structures are moved relative to eachother. With this configuration, the load can be reduced during the stopperiod, a predetermined amount of time before the start of the driveperiod.

In the above wind turbine drive control device, the predetermined timingmay be a timing reached a predetermined amount of time after an end of adrive period in which the two structures are moved relative to eachother. With this configuration, the load can be reduced during the stopperiod, a predetermined amount of time after the end of the driveperiod.

In the above wind turbine drive control device, the at least one drivedevice may comprise a plurality of drive devices, each controlled by thewind turbine drive control device. In this case, the obtaining unitobtains information related to the load occurring between each of theplurality of drive devices and one of the two structures that receivesforces generated by the plurality of drive devices, and the control unitcontrols the plurality of drive devices so as to cause a force generatedby at least one of the plurality of drive devices to be reduced or zerobased on the information related to the load obtained by the obtainingunit during the stop period in which the two structures are stoppedrelative to each other. With this configuration, the load can be reducedduring the stop period in accordance with the information related to theload.

To achieve the above object, a wind turbine drive control deviceaccording to one aspect of the present invention is a wind turbine drivecontrol device for controlling a plurality of drive devices eachincluding a brake unit and a drive unit, the brake unit being configuredto generate a braking force for stopping a second structure relative toa first structure, both the first and second structures being includedin a wind power generation device, the drive unit being configured togenerate a drive force for moving the second structure relative to thefirst structure, the wind turbine drive control device comprising: acontrol unit configured to switch between a drive period in which thesecond structure is moved relative to the first structure and a stopperiod in which the second structure is stopped relative to the firststructure, the control unit being further configured to control theplurality of drive devices so as to cause a force generated by at leastone of the plurality of drive devices to be reduced or zero when apredetermined timing is reached during the stop period. With thisconfiguration, the load can be reduced during the stop period inaccordance with the information related to the load.

To achieve the above object, a control method according to one aspect ofthe present invention is a control method of a wind turbine drivedevice, for controlling a drive device for moving two structuresincluded in a wind power generation device relative to each other, thecontrol method comprising: obtaining information related to a loadoccurring between the drive device and one of the two structures thatreceives a force generated by the drive device; and controlling thedrive device so as to cause a force generated by the drive device to bereduced or zero based on the information related to the load during astop period in which the two structures are stopped relative to eachother. With this method, the load can be reduced during the stop periodin accordance with the information related to the load.

To achieve the above object, a control method according to one aspect ofthe present invention is a control method of a wind turbine drivedevice, for controlling a drive device for moving two structuresincluded in a wind power generation device relative to each other, thecontrol method comprising: controlling the drive device so as to cause aforce generated by the drive device to be reduced or zero when apredetermined timing is reached during a stop period in which the twostructures are stopped relative to each other. With this method, theload can be reduced during the stop period in accordance with theinformation related to the load.

Advantageous Effects

According to one aspect of the present invention, the load occurring inthe stop period can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an example of a wind powergeneration device according to an embodiment of the present invention.

FIG. 2 is a top view showing a relationship between the tower and theyaw drive devices according to the embodiment.

FIG. 3 shows an example of the yaw drive device according to theembodiment.

FIG. 4 is a block diagram showing an example of functionality of thewind power generation device according to the embodiment.

FIG. 5 shows periods of control according to the embodiment.

FIG. 6 is a flowchart showing an example of control based on the loadduring a stop period according to the embodiment.

FIG. 7 shows an example of operation for controlling the braking forceaccording to the embodiment. Part (A) of FIG. 7 shows a change in acontrol signal provided to a motor brake unit. Part (B) of FIG. 7 showsa change in the braking force on a ring gear.

FIG. 8 shows another example of operation for controlling the brakingforce according to the embodiment. Part (A) of FIG. 8 shows a change ina control signal provided to a motor drive unit. Part (B) of FIG. 8shows a change in a control signal provided to the motor brake unit (anelectromagnetic brake). Part (C) of FIG. 8 shows a change in a controlsignal provided to a hydraulic brake driving unit 52.

FIG. 9 shows another example of operation for controlling the brakingforce according to the embodiment. Part (A) of FIG. 9 shows a change ina control signal provided to the motor drive unit. Part (B) of FIG. 9shows a change in a control signal provided to the motor brake unit (anelectromagnetic brake). Part (C) of FIG. 9 shows a change in a controlsignal provided to the hydraulic brake driving unit 52.

FIG. 10 shows another example of operation for controlling the brakingforce according to the embodiment. Part (A) of FIG. 10 shows a change ina control signal provided to the motor drive unit. Part (B) of FIG. 10shows a change in a control signal provided to the motor brake unit (anelectromagnetic brake). Part (C) of FIG. 10 shows a change in a controlsignal provided to the hydraulic brake driving unit 52.

FIG. 11 shows another example of operation for controlling the brakingforce according to the embodiment. Part (A) of FIG. 11 shows a change ina control signal provided to the motor drive unit. Part (B) of FIG. 11shows a change in a control signal provided to the motor brake unit (anelectromagnetic brake). Part (C) of FIG. 11 shows a change in a controlsignal provided to the hydraulic brake driving unit 52.

FIG. 12 shows another example of operation for controlling the brakingforce according to the embodiment. Part (A) of FIG. 12 shows a change ina control signal provided to the motor brake unit in a yaw drive device100-1. Part (B) of FIG. 12 shows a change in a control signal providedto the motor brake unit in a yaw drive device 100-2. Part (C) of FIG. 12shows a change in a control signal provided to the motor brake unit in ayaw drive device 100-3. Part (D) of FIG. 12 shows a change in a controlsignal provided to the motor brake unit 160 in a yaw drive device 100-4.

FIG. 13 shows another example of operation for controlling the brakingforce according to the embodiment. Part (A) of FIG. 13 shows a change ina control signal provided to the motor brake unit in the yaw drivedevice 100-1. Part (B) of FIG. 13 shows a change in a control signalprovided to the motor brake unit in the yaw drive device 100-2. Part (C)of FIG. 13 shows a change in a control signal provided to the motorbrake unit in the yaw drive device 100-3. Part (D) of FIG. 13 shows achange in a control signal provided to the motor brake unit 160 in theyaw drive device 100-4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the drawings, the following describes a wind turbinedrive control device and a control method of a wind turbine drive deviceaccording to the embodiment.

FIG. 1 is a perspective view showing an example of a wind powergeneration device according to an embodiment of the present invention.The wind power generation device 1 includes, for example, a nacelle 10,a tower 20, a blade 30, and a hub 40. The tower 20 and the nacelle 10are examples of two structures included in the wind power generationdevice 1. The tower 20 and the nacelle 10 move relative to each other bya force from drive devices (yaw drive devices 100). The tower 20 is anexample of a first structure that is a part of the wind power generationdevice 1 installed fixedly. The nacelle 10 is an example of a secondstructure that moves relative to the first structure by the drive forcefrom the yaw drive devices 100 and stops relative to the first structureby the braking force from the yaw drive devices 100.

The nacelle 10 is mounted on the top end (the end in the Z direction) ofthe tower 20. The blade 30 is mounted to the nacelle 10 via the hub 40.The nacelle 10 turns to adjust the orientation of the blade 30 and thehub 40 in the yaw direction. The nacelle 10 includes yaw drive devicesfor generating a yaw drive force for rotating the nacelle 10 in the yawdirection. The yaw drive devices are an example of drive devices andwind turbine drive devices. The drive devices and the wind turbine drivedevices generate a force for rotating the orientation of the blade 30and the hub 40 (the orientation of a wind turbine) in accordance withthe wind direction. The tower 20 is embedded on the land or on the sea.The tower 20 extends upward in a vertical direction from the land or thesea. The nacelle 10 is mounted on the top end of the tower 20. The tower20 includes a blade gear (not shown) for driving the turning of thenacelle 10 in the yaw direction. The nacelle 10 is an example of astructure not provided with a force generated by the drive devices. Thetower 20 is an example of a structure provided with a force generated bythe drive devices.

The blade 30 receives wind force and generates a rotational force. Inthe embodiment, three blades 30 are provided.

The hub 40 is mounted to the nacelle 10, and a plurality of blades 30are mounted to the hub 40. The hub 40 transmits to a rotating shaft therotational force (motive power) generated by the wind force received bythe blades 30. The hub 40 transmits the rotational force based on thewind force to the nacelle 10 via the rotating shaft.

The hub 40 includes pitch drive mechanisms for generating a pitch driveforce for rotating the blades 30 in the pitch direction. Each blade 30is provided with a drive mechanism for generating a pitch drive force.The pitch drive mechanisms rotate the blades 30 in the pitch directionto control the angles of the blades 30 in accordance with the windvelocity.

In the wind power generation device 1, the motive power generated by therotation of the blades 30 is transmitted from the hub 40 to a powergenerator (not shown) in the nacelle 10 and converted into an electricpower. In this way, the wind power generation device 1 performs windpower generation.

FIG. 2 is a top view showing a relationship between the tower and theyaw drive devices according to the embodiment. The yaw drive devices 100for generating the yaw drive force are mounted to the nacelle 10. In theembodiment, four yaw drive devices 100-1, 100-2, 100-3, and 100-4 aremounted to the nacelle 10. These yaw drive devices may be hereinaftercollectively referred to simply as “the yaw drive devices 100.” In FIG.2, a ring gear 22 is formed in the inner wall of the tower 20. The ringgear 22 meshes with pinion gears 150 of the yaw drive devices 100. Theyaw drive devices 100 revolve in the R direction in FIG. 2 by the motordrive force. The yaw drive devices 100 may also be able to revolve inthe opposite direction to the R direction.

With the ring gear 22 and the pinion gears 150 meshing with each other,a force such as a gust of wind applied to the nacelle 10, the tower 20or the like generates a tangential force between the ring gear 22 andthe pinion gears 150. The tangential force is a force generated in thetangential direction of the gear forming surface of the ring gear 22.The tangential force applies a torsional stress to a speed reducing unitof each of the yaw drive devices 100. The tangential force applies atensile stress and a compressive stress to a fastener in each of the yawdrive devices 100. In the embodiment, the ring gear 22 is provided inthe tower 20 and the yaw drive devices 100 are fixed to the nacelle 10,but this example is not limitative. It is also possible that the nacelle10 includes a gear portion corresponding to the ring gear 22, and thetower 20 includes yaw drive devices corresponding to the yaw drivedevices 100.

FIG. 3 shows an example of the yaw drive device according to theembodiment. The yaw drive device 100 includes, for example, a casing110, a flange 120, fastening bolts 130, an output shaft 140, and apinion gear 150. The flange 120 is mounted to the casing 110. The flange120 is connected to the nacelle 10 with the fastening bolts 130. One endof the output shaft 140 is connected to the interior of the casing 110and the flange 120, and the other end of the output shaft 140 has thepinion gear 150 provided thereon. The pinion gear 150 is positioned soas to mesh with the ring gear 22. The pinion gear 150 rotates by thedrive force output from the output shaft 140 to cause the yaw drivedevice 100 to revolve in the revolving direction (device movementdirection or reverse X direction). The yaw drive device 100 in turncauses the nacelle 10 to turn relative to the tower 20. The fasteningbolts 130 are an example of the fasteners. The fasteners are elementsfor fixing the yaw drive device 100 to the nacelle 10. The fasteners arenot limited to the fastening bolts 130 but may be other known members.The output shaft 140 and the pinion gear 150 are an example of atransmission unit. The transmission unit is an element for transmittinga drive force and a braking force from the yaw drive device 100 to thetower 20. If the drive device is fixed to the tower 20, the transmissionunit is an element for transmitting the forces from the tower 20 to thenacelle 10.

The yaw drive device 100 includes a motor brake unit 160, a motor driveunit 162, and a speed reducing unit 164. The motor brake unit 160generates a braking force for the output shaft 140. The motor brake unit160 applies the braking force directly to the output shaft 140, but thisis not limitative. It is also possible that the braking force is appliedindirectly to the output shaft 140. For example, the force of the motorbrake unit 160 may be applied to a member other than the output shaft140 and then applied to the output shaft 140 from this member. The motordrive unit 162 generates a drive force for the output shaft 140. Themotor brake unit 160 generates the braking force by an electromagneticaction in accordance with a control signal provided externally. Themotor brake unit 160 serves as an electromagnetic brake. The motor driveunit 162 generates the drive force by an electromagnetic action inaccordance with a control signal provided externally. The speed reducingunit 164 reduces the rotation speed according to the drive forcegenerated by the output shaft 140 to increase the drive torque. Themotor brake unit 160 and/or the motor drive unit 162 are an example of aforce generation unit. The force generation unit generates a force. Atleast one of the yaw drive devices 100 is an example of the drivedevice. In the drive device, the force generation unit generates theforce that is then transmitted to the transmission unit. In theembodiment, the yaw drive device 100 generate the drive force and thebraking force, but this is not limitative. It is also possible to obtaina braking force by generating a drive force in an opposite direction tothe direction of the drive force for rotating the nacelle 10. In such acase, the yaw drive device 100 does not need to include the motor brakeunit 160.

Further, the yaw drive device 100 includes a strain sensor 166 a and astrain sensor 166 b. The strain sensors 166 are an example of anobtaining unit for obtaining information on the load. The strain sensor166 a and the strain sensor 166 b may be hereinafter collectivelyreferred to simply as “the strain sensors 166.” The strain sensors 166output a signal in accordance with a strain occurring in the fasteningbolts 130. The strain occurring in the fastening bolts 130 changes inaccordance with the tangential force. In the embodiment, the strain inthe fastening bolts 130 is detected as the information on the load, butthis is not limitative. It is also possible to detect a torque occurringbetween the output shaft 140 and the ring gear 22. In the yaw drivedevice 100, for example, the torque may be detected by measuring theamount of force acting on the output shaft 140. Further, the yaw drivedevice 100 may include a torque meter for sensing torsion in the outputshaft 140 that connects between the motor drive unit 162 and the motorbrake unit 160, such that an output signal from the torque meter can beobtained as information on the load. Further, the yaw drive device 100may include a strain gauge disposed at the base of a gear such as thepinion gear 150 for transmitting the drive force or the braking force,such that an output signal from the strain gauge can be obtained asinformation on the load. Further, in the yaw drive device 100, adifference between the output torsion angle of the output shaft 140 andan input torsion angle of the output shaft 140 may be sensed, such thatthe information indicating the sensed difference can be obtained asinformation on the load. The output torsion angle of the output shaft140 is a torsion angle of the output shaft 140 near the motor brake unit160 or the motor drive unit 162, and the input torsion angle of theoutput shaft 140 is a torsion angle of the output shaft 140 near thepinion gear 150.

The wind power generation device 1 includes a hydraulic brake forapplying a braking force to the ring gear 22. The hydraulic brake is,for example, a caliper brake mechanism. The hydraulic brake includes ahydraulic brake driving unit 52 and a friction member 50. The hydraulicbrake driving unit 52 moves the friction member 50 in the Z direction inFIG. 3 in accordance with a control signal provided externally. Thehydraulic brake driving unit 52 applies a braking force to the ring gear22 by urging the friction member 50 against the ring gear 22. The windpower generation device 1 is preferably capable of adjusting the brakingforce applied to the ring gear 22.

FIG. 4 is a block diagram showing an example of functionality of thewind power generation device according to the embodiment. FIG. 4 showsan example of functionality for controlling the yaw drive force in thewind power generation device 1. The wind power generation device 1includes, for example, a control unit 170, strain sensors 166-1, 166-2,166-3, 166-4, motor drive/brake units 160/162-1, 160/162-2, 160/162-3,160/162-4, a hydraulic brake driving unit 52, and a wind sensor 200.

The strain sensor 166-1 corresponds to the strain sensor 166 a and thestrain sensor 166 b in the yaw drive device 100-1. The strain sensor166-2 corresponds to the strain sensor 166 a and the strain sensor 166 bin the yaw drive device 100-2. The strain sensor 166-3 corresponds tothe strain sensor 166 a and the strain sensor 166 b in the yaw drivedevice 100-3. The strain sensor 166-4 corresponds to the strain sensor166 a and the strain sensor 166 b in the yaw drive device 100-4. Each ofthe yaw drive devices 100 may include more than one strain sensors 166.

The motor drive/brake unit 160/162-1 corresponds to the motor brake unit160 and the motor drive unit 162 in the yaw drive device 100-1. Themotor drive/brake unit 160/162-2 corresponds to the motor brake unit 160and the motor drive unit 162 in the yaw drive device 100-2. The motordrive/brake unit 160/162-3 corresponds to the motor brake unit 160 andthe motor drive unit 162 in the yaw drive device 100-3. The motordrive/brake unit 160/162-4 corresponds to the motor brake unit 160 andthe motor drive unit 162 in the yaw drive device 100-4.

The wind sensor 200 is disposed, for example, on the top surface of thenacelle 10. The wind sensor 200 generates a signal (wind sensing signal)that indicates the wind strength and the wind direction and providesthis signal to the control unit 170.

The control unit 170 is formed of, for example, a processor such as aCPU (Central Processing Unit) executing a program stored on a programmemory. The control unit 170 may alternatively be formed of hardwaresuch as a LSI (Large Scale Integration), an ASIC (Application SpecificIntegrated Circuit), or a FPGA (Field-Programmable Gate Array) or formedof software and hardware cooperating with each other. The control unit170 receives a strain sensing signal from each of the strain sensors166-1, 166-2, 166-3, and 166-4. The control unit 170 receives a windsensing signal from the wind sensor 200. The control unit 170 outputscontrol signals to the motor drive/brake units 160/162-1, 160/162-2,160/162-3, 160/162-4, and the hydraulic brake driving unit 52 based onthe strain sensing signals and the wind sensing signal. The control unit170 is an example of the wind turbine drive control device that causesthe forces generated by the yaw drive devices 100 to be reduced or zero,but alternatively, the control unit 170 and the strain sensors 166 maybe an example of the wind turbine drive control device.

FIG. 5 shows periods of control according to the embodiment. As shown inFIG. 5 for example, the control unit 170 previously sets a drive periodand a stop period. In the drive period, the orientation of the nacelle10 is moved based on the direction of wind. In the stop period, theorientation of the nacelle 10 is fixed. In other words, the stop periodis a period in which the two structures included in the wind powergeneration device are stopped relative to each other. During the driveperiod, the control unit 170 performs control for moving the nacelle 10to a target position relative to the tower 20. During the stop period,the control unit 170 performs control for stopping the nacelle 10 at atarget position relative to the tower 20. The target position is theoptimal position of the nacelle 10 relative to the tower 20 determinedbased on the wind direction.

At the timing of starting the drive period, the control unit 170 startscontrol for moving the nacelle 10 to the target position relative to thetower 20. The control unit 170 positions the nacelle 10 at the targetposition by the timing of ending the drive period. The control unit 170causes the braking force to be generated so as to fix the nacelle 10 atthe target position during the stop period. In this way, the controlunit 170 switches the control between the drive period and the stopperiod.

The following describes the control in the yaw drive device 100 duringthe period in which the nacelle 10 (the second structure) is to bestopped relative to the tower 20 (the first structure). FIG. 6 is aflowchart showing an example of control based on the load during a stopperiod according to the embodiment. The control unit 170 firstdetermines whether or not a stop period is ongoing (step S10). If a stopperiod is not ongoing at present (No in step S10), the control unit 170ends the process of this flowchart. If the control unit 170 determinesthat a stop period is ongoing at present (Yes in step S10), then itdetermines whether or not the load is equal to or larger than athreshold value (step S12). The load is the values of the strain sensingsignals obtained by the strain sensors 166, but this is not limitative.The load may be a value that impacts on the load occurring between thering gear 22 and the pinion gear 150. For example, the load mayalternatively be the wind strength sensed by the wind sensor 200. Thethreshold value is the upper limit of the strain sensing signals, butthis is not limitative. The threshold value may alternatively be theupper limit of the wind strength.

If the load is not equal to or larger than the threshold value, thecontrol unit returns to step S10. If the load is equal to or larger thanthe threshold value (Yes in step S12), the control unit 170 performscontrol to cause the force of the electromagnetic brake to be reduced orzero (step S14). In step S14, the control unit 170 causes the brakingforce of the electromagnetic brake to be reduced or zero, for example,for a period sufficiently shorter than the stop period or the driveperiod (e.g., several micro seconds). The operation in step S14 may beread as temporarily causing the force of the electromagnetic brake to bereduced or zero or read as stopping the operation of the electromagneticbrake.

FIG. 7 shows an example of operation for controlling the braking forceaccording to the embodiment. Part (A) of FIG. 7 shows a change in acontrol signal provided to the motor brake unit 160. Part (B) of FIG. 7shows a change in the braking force on the ring gear 22. Suppose that,in the wind power generation device 1, the ring gear 22 receives abraking force F1 that is a sum of the braking forces provided by themotor brake units 160 (electromagnetic brakes) and the braking forceprovided by the friction member 50. The braking force F1 is a brakingforce necessary to stop rotation of the pinion gears 150 and fix thepinion gears 150 to the ring gear 22.

In the wind power generation device 1, if it is determined that the loadis equal to or larger than the threshold value during the stop period,the electromagnetic brakes are temporarily stopped. At this time, thecontrol unit 170 provides a pulse signal to the motor brake units 160.In response to the pulse signal provided, the motor brake units 160reduce the braking forces generated by the electromagnetic action. Inthis way, the braking forces of the electromagnetic brakes aretemporarily removed, with the pinion gears 150 meshing freely with thering gear 22, and the ring gear 22 temporarily receiving only thebraking force F2 applied by the friction member 50. If the forcecorresponding to the load between the pinion gears 150 and the ring gear22 does not exceed the braking force F2, the nacelle 10 is retained bythe braking force F2, and the load accumulated in the speed reducingunits 164 is reduced. If the force corresponding to the load between thepinion gears 150 and the ring gear 22 exceeds the braking force F2, thenacelle 10 is rotated. However, since the pinion gears 150 mesh freelywith the ring gear 22, the rotation of the nacelle 10 does not cause theload to be accumulated in the speed reducing units 164. Thus, the loadafter revolution of the yaw drive devices 100 falls below the loadbefore removal of the braking forces of the electromagnetic brakes. As aresult, the wind power generation device 1 is capable of inhibiting amalfunction due to a change in the load during the stop period.

The phrase “reducing the braking force” encompasses reducing the currentbraking force of the electromagnetic brake to a value larger than zeroand setting the current braking force of the electromagnetic brake atzero. The processes for reducing the braking force include a process ofswitching a control signal provided to the motor brake unit 160 from ONto OFF and a process of performing duty control of the control signal toreduce the amount of electric power necessary for the braking force ofthe electromagnetic brake.

By way of an example, the drive period may be several minutes, and thestop period may be ten-odd minutes. The period in which the brakingforce of the electromagnetic brake is temporarily reduced may be, forexample, several micro seconds. The period in which the pulse signal isON, which corresponds to the period in which the braking force of theelectromagnetic brake is reduced, may be, for example, several microseconds.

FIG. 8 shows another example of operation for controlling the brakingforce according to the embodiment. Part (A) of FIG. 8 shows a change ina control signal provided to the motor drive unit 162. Part (B) of FIG.8 shows a change in a control signal provided to the motor brake unit160 (the electromagnetic brake). Part (C) of FIG. 8 shows a change in acontrol signal provided to the hydraulic brake driving unit 52.

The yaw drive device 100 may temporarily reduce the braking force of theelectromagnetic brake when a predetermined timing (t1) is reached duringthe period in which the nacelle 10 is stopped relative to the tower 20.The predetermined timing may be reached, for example, at regularintervals within the stop period. The yaw drive device 100 then reducesthe braking force of the hydraulic brake at time t2 within the driveperiod, and the yaw drive device 100 reduces the braking force of theelectromagnetic brake and causes the drive force to be generated at timet3. The yaw drive device 100 stops the drive of the motor drive unit 162and causes the braking force to be generated at time t4 within the driveperiod, and then actuates the braking force of the hydraulic brake attime t5. In this way, even when there is possibility that a large loadoccurs between the ring gear 22 and the pinion gear 150 due to a gust ofwind during the stop period after the drive period, the yaw drive device100 may temporarily reduce the braking force of the electromagneticbrake to reduce the load. The yaw drive device 100 is thus capable ofpreventing a large load without sensing the load between the ring gear22 and the pinion gear 150.

FIG. 9 shows another example of operation for controlling the brakingforce according to the embodiment. Part (A) of FIG. 9 shows a change ina control signal provided to the motor drive unit 162. Part (B) of FIG.9 shows a change in a control signal provided to the motor brake unit160 (the electromagnetic brake). Part (C) of FIG. 9 shows a change in acontrol signal provided to the hydraulic brake driving unit 52.

The yaw drive device 100 may temporarily reduce the braking force of theelectromagnetic brake when a predetermined timing (t10) before the startof the drive period is reached during the period in which the nacelle 10is stopped relative to the tower 20. The yaw drive device 100 thenreduces the braking force of the hydraulic brake at time t2 within thedrive period, and the yaw drive device 100 reduces the braking force ofthe electromagnetic brake and causes the drive force to be generated attime t3. The yaw drive device 100 stops the drive of the motor driveunit 162 and causes the braking force to be generated at time t4 withinthe drive period, and then actuates the braking force of the hydraulicbrake at time t5. In this way, the yaw drive device 100 is preventedfrom driving the pinion gear 150 under a large load received during thestop period. As a result, the yaw drive device 100 is prevented fromhaving a malfunction occurring when the drive of the pinion gear 150 isstarted.

FIG. 10 shows another example of operation for controlling the brakingforce according to the embodiment. Part (A) of FIG. 10 shows a change ina control signal provided to the motor drive unit 162. Part (B) of FIG.10 shows a change in a control signal provided to the motor brake unit160 (the electromagnetic brake). Part (C) of FIG. 10 shows a change in acontrol signal provided to the hydraulic brake driving unit 52.

The yaw drive device 100 may temporarily reduce the braking force of theelectromagnetic brake when a predetermined timing (t20) after the end ofthe drive period is reached during the period in which the nacelle 10 isstopped relative to the tower 20. This operation inhibits and eliminatesthe variation of the loads among the yaw drive devices 100 caused by thedifference in the brake timing and variation in the meshing conditionamong the yaw drive devices 100. As a result, the load can be uniformedamong the yaw drive devices 100.

The control operations referring to FIGS. 8, 9, and 10 may be combinedtogether. Specifically, the control unit 170 may temporarily reduce thebraking force of the electromagnetic brake at at least one of a timingreached at regular intervals, a timing reached before the start of thedrive period, and a timing reached after the end of the drive period,during the period in which the nacelle 10 is stopped relative to thetower 20.

FIG. 11 shows another example of operation for controlling the brakingforce according to the embodiment. Part (A) of FIG. 11 shows a change ina control signal provided to the motor drive unit 162. Part (B) of FIG.11 shows a change in a control signal provided to the motor brake unit160 (the electromagnetic brake). Part (C) of FIG. 11 shows a change in acontrol signal provided to the hydraulic brake driving unit 52. When apredetermined timing is reached, the control unit 170 may provide apulse signal to the motor brake unit 160 (the electromagnetic brake) fora plurality of times. The control unit 170 may provide a pulse signal tothe motor brake unit 160 (the electromagnetic brake) for a plurality oftimes at preset pulse intervals. Alternatively, the control unit 170 mayprovide a pulse signal to the motor brake unit 160 (the electromagneticbrake) for a plurality of times until the value based on the load sensedby the strain sensors 166 falls below a threshold value. In this way,the yaw drive device 100 can divide the operation for reducing the loadinto a plurality of runs. The process for controlling the braking forcemay include a process of performing duty control of the control signalprovided to the electromagnetic brake. This can reduce the amount ofelectric power supplied to the electromagnetic brake, thereby to causethe force generated by the electromagnetic brake to be reduced or zero.

FIGS. 12 and 13 show another example of operation for controlling thebraking force according to the embodiment. Part (A) of FIG. 12 and Part(A) of FIG. 13 show a change in a control signal provided to the motorbrake unit 160 in the yaw drive device 100-1. Part (B) of FIG. 12 andPart (B) of FIG. 13 show a change in a control signal provided to themotor brake unit 160 in the yaw drive device 100-2. Part (C) of FIG. 12and Part (C) of FIG. 13 show a change in a control signal provided tothe motor brake unit 160 in the yaw drive device 100-3. Part (D) of FIG.12 and Part (D) of FIG. 13 show a change in a control signal provided tothe motor brake unit 160 in the yaw drive device 100-4. As shown in FIG.12, when a predetermined timing is reached, the control unit 170 mayprovide a control signal to a plurality of motor brake units 160 toreduce the braking forces. As shown in FIG. 13, when a predeterminedtiming is reached, the control unit 170 may provide a control signal toa part of a plurality of motor brake units 160 to reduce the brakingforces. When the load is equal to or larger than the threshold value,the control unit 170 may provide a control signal to all or a part ofthe motor brake units 160 to reduce the braking forces.

According to the embodiment described above, it is possible to realize awind turbine drive control device for controlling at least one yaw drivedevice 100 for moving two structures (the nacelle 10 and the tower 20)included in a wind power generation device 1 relative to each other, thewind turbine drive control device comprising: an obtaining unit 166 forobtaining information related to a load occurring between the at leastone yaw drive device 100 and one of the two structures that receives aforce generated by the at least one yaw drive device 100; and a controlunit 170 for controlling the at least one yaw drive device 100 so as tocause a force generated by the at least one yaw drive device 100 to bereduced or zero based on the information related to the load obtained bythe obtaining unit during a stop period in which the two structures arestopped relative to each other. In this way, according to theembodiment, the load occurring between the nacelle 10 and the tower 20can be reduced during the stop period.

According to the embodiment, even when the control unit 170 performscontrol for switching between the drive period in which the nacelle 10is moved to the target position and the stop period in which the nacelle10 is stopped at the target position, the braking force can betemporarily reduced during the stop period in which the braking forceshould not be reduced.

According to the embodiment, the information related to the load isbased on the force acting on the strain sensors 166 that fix the yawdrive device 100 to one of the two structures, and therefore, theinformation related to the load can be obtained using the force actingon the strain sensors 166.

According to the embodiment, it is possible to realize a wind turbinedrive control device for controlling at least one yaw drive device 100for moving two structures included in a wind power generation device 1relative to each other, the wind turbine drive control devicecomprising: a control unit 170 for controlling the at least one yawdrive device 100 so as to cause a force generated by the at least oneyaw drive device 100 to be reduced or zero when a predetermined timingis reached during a stop period in which the two structures are stoppedrelative to each other. With this configuration, the load occurring inthe stop period can be reduced before the stop period is ended.According to this embodiment, the load can be uniformly distributed to aplurality of yaw drive devices 100, and thus a large load occurring inthe stop period is not concentrated on a particular yaw drive device100. Further, according to the embodiment, the lives of the yaw drivedevices 100 and the ring gear 22 can be prolonged by uniformlydistributing the load to the plurality of yaw drive devices 100 ratherthan by inhibiting an excess load from occurring in a particular yawdrive device 100.

According to the embodiment, the predetermined timing is a timingreached at regular intervals within the stop period, and therefore, theload occurring in the stop period can be reduced at regular intervals.

According to the embodiment, the predetermined timing is a timingreached a predetermined amount of time before a start of the driveperiod in which the two structures are moved relative to each other, andtherefore, the load can be reduced during the stop period, apredetermined amount of time before the start of the drive period. Inthis way, according to the embodiment, it can be prevented to startdriving under a large load.

According to the embodiment, the predetermined timing is a timingreached a predetermined amount of time after an end of the drive periodin which the two structures are moved relative to each other, andtherefore, the load can be reduced during the stop period, apredetermined amount of time after the end of the drive period. Thisoperation reduces the variation of the loads among the yaw drive devices100 caused by the difference in the brake timing and variation in themeshing condition among the yaw drive devices 100.

According to the embodiment, it is possible to realize a wind turbinedrive control device for controlling a plurality of yaw drive devices100 for moving two structures included in a wind power generation device1 relative to each other, the wind turbine drive control devicecomprising: an obtaining unit 166 for obtaining information related to aload occurring between each of the plurality of yaw drive devices 100and one of the two structures that receives forces generated by theplurality of yaw drive devices 100; and a control unit 170 forcontrolling the plurality of yaw drive devices 100 so as to cause aforce generated by at least one of the plurality of yaw drive devices100 to be reduced or zero based on the information related to the loadobtained by the obtaining unit 166 during a stop period in which the twostructures are stopped relative to each other. According to theembodiment, the load can be reduced during the stop period in accordancewith the information related to the load.

According to the embodiment, it is possible to realize a wind turbinedrive control device for controlling a plurality of yaw drive devices100 each including a motor brake unit 160 and a motor drive unit 162,the motor brake unit 160 being configured to generate a braking forcefor stopping the nacelle 10 relative to the tower 20, both the nacelle10 and the tower 20 being included in a wind power generation device,the motor drive unit 162 being configured to generate a drive force formoving the nacelle 10 relative to the tower 20, the wind turbine drivecontrol device comprising: a control unit 170 configured to switchbetween a drive period in which the nacelle 10 is moved relative to thetower 20 and a stop period in which the nacelle 10 is stopped relativeto the tower 20, the control unit 170 being further configured tocontrol the plurality of yaw drive devices 100 so as to cause a forcegenerated by at least one of the plurality of yaw drive devices 100 tobe reduced or zero when a predetermined timing is reached during thestop period. According to the embodiment, the load can be reduced duringthe stop period in accordance with the information related to the load.

According to the embodiment, it is possible to realize a control methodof a wind turbine drive device, for controlling a yaw drive device 100for moving two structures (10, 20) included in a wind power generationdevice 1 relative to each other, the control method comprising:obtaining information related to a load occurring between the yaw drivedevice 100 and one of the two structures (10, 20) that receives a forcegenerated by the yaw drive device 100; and controlling the yaw drivedevice 100 so as to cause a force generated by the yaw drive device 100to be reduced or zero based on the information related to the loadduring a stop period in which the two structures (10, 20) are stoppedrelative to each other. With this method, the load can be reduced duringthe stop period in accordance with the information related to the load.

According to the embodiment, it is possible to realize a control methodof a wind turbine drive device, for controlling a yaw drive device 100for moving two structures (10, 20) included in a wind power generationdevice 1 relative to each other, the control method comprising:controlling the yaw drive device 100 so as to cause a force generated bythe yaw drive device 100 to be reduced or zero when a predeterminedtiming is reached during a stop period in which the two structures (10,20) are stopped relative to each other. With this method, the load canbe reduced during the stop period in accordance with the informationrelated to the load.

The functions of the control unit 170 according to the embodimentdescribed above may be implemented in a program stored on acomputer-readable storage medium, and the program stored on the storagemedium may be loaded onto a computer system that then executes theprogram for processing. The “computer system” mentioned above mayinclude an operating system (OS) or hardware such as peripheral devices.The “computer-readable storage medium” mentioned above refers to astorage device such as a portable medium like a flexible disc, amagneto-optical disc, a ROM (Read Only Memory), a flash memory or otherwritable non-volatile memory, and a DVD (Digital Versatile Disc), and ahard disk built-in to the computer system.

Further, the “computer-readable storage medium” includes storage mediathat retain the program for some period of time, like a volatile memory(for example, DRAM (Dynamic Random Access Memory)) in an informationprocessing device receiving the program through a network such as theInternet or a communication line such as a telephone line, and acomputer system that operates as a client. The computer programmentioned above may be transmitted from a computer system that includesa storage device or the like storing the program to another computersystem through a transmission medium or by a transmission wave in atransmission medium. The “transmission medium” for transmitting theprogram refers to a medium that operates to transmit information, like anetwork (communication network) such as the Internet or a communicationline (communication wire) such as the telephone line. Only a part of thefunctions described above may be implemented in the above program.Further, the functions described above may be implemented by acombination of the above program and programs previously stored on thecomputer system. That is, the above program may be what is called adifference file (a difference program). The foregoing is the descriptionof the embodiments of the present invention with reference to thedrawings. Specific configurations are not limited to the aboveembodiments but include design modifications within the purport of thepresent invention.

What is claimed is:
 1. A wind turbine drive control device forcontrolling at least one drive device for moving two structures includedin a wind power generation device relative to each other, the windturbine drive control device comprising: an obtaining unit for obtaininginformation related to a load occurring between the at least one drivedevice and one of the two structures that receives a force generated bythe at least one drive device; and a control unit for controlling the atleast one drive device so as to cause a force generated by the at leastone drive device to be reduced or zero based on the information relatedto the load obtained by the obtaining unit during a stop period in whichthe two structures are stopped relative to each other.
 2. The windturbine drive control device of claim 1, wherein the information relatedto the load is information based on a force acting on a fastener fixingthe at least one drive device to one of the two structures.
 3. A windturbine drive control device for controlling at least one drive devicefor moving two structures included in a wind power generation devicerelative to each other, the wind turbine drive control devicecomprising: a control unit for controlling the at least one drive deviceso as to cause a force generated by the at least one drive device to bereduced or zero when a predetermined timing is reached during a stopperiod in which the two structures are stopped relative to each other.4. The wind turbine drive control device of claim 3, wherein thepredetermined timing is a timing reached at regular intervals within thestop period.
 5. The wind turbine drive control device of claim 3,wherein the predetermined timing is a timing reached a predeterminedamount of time before a start of a drive period in which the twostructures are moved relative to each other.
 6. The wind turbine drivecontrol device of claim 3, wherein the predetermined timing is a timingreached a predetermined amount of time after an end of a drive period inwhich the two structures are moved relative to each other.
 7. The windturbine drive control device of claim 1, wherein the at least one drivedevice comprises a plurality of drive devices, each controlled by thewind turbine drive control device, wherein the obtaining unit obtainsinformation related to the load occurring between each of the pluralityof drive devices and one of the two structures that receives forcesgenerated by the plurality of drive devices, and wherein the controlunit controls the plurality of drive devices so as to cause a forcegenerated by at least one of the plurality of drive devices to bereduced or zero based on the information related to the load obtained bythe obtaining unit during the stop period in which the two structuresare stopped relative to each other.
 8. The wind turbine drive controldevice of claim 3, wherein the at least one drive device comprises aplurality of drive devices, each controlled by the wind turbine drivecontrol device, and wherein the control unit controls the plurality ofdrive devices so as to cause a force generated by at least one of theplurality of drive devices to be reduced or zero when a predeterminedtiming is reached during the stop period in which the two structures arestopped relative to each other.
 9. A wind turbine drive control devicefor controlling a plurality of drive devices each including a brakeunit, a drive unit, and a transmission unit, the brake unit beingconfigured to generate a braking force for stopping a second structurerelative to a first structure, both the first and second structuresbeing included in a wind power generation device, the drive unit beingconfigured to generate a drive force for moving the second structurerelative to the first structure, the transmission unit being configuredto transmit the braking force and the drive force to the firststructure, the wind turbine drive control device comprising: anobtaining unit for obtaining information based on a force acting on afastener fixing the plurality of drive devices to the second structure;and a control unit configured to switch between a drive period in whichthe second structure is moved relative to the first structure and a stopperiod in which the second structure is stopped relative to the firststructure, the control unit being further configured to control theplurality of drive devices so as to cause a force generated by at leastone of the plurality of drive devices to be reduced or zero based on theinformation obtained by the obtaining unit during the stop period.
 10. Awind turbine drive control device for controlling a plurality of drivedevices each including a brake unit and a drive unit, the brake unitbeing configured to generate a braking force for stopping a secondstructure relative to a first structure, both the first and secondstructures being included in a wind power generation device, the driveunit being configured to generate a drive force for moving the secondstructure relative to the first structure, the wind turbine drivecontrol device comprising: a control unit configured to switch between adrive period in which the second structure is moved relative to thefirst structure and a stop period in which the second structure isstopped relative to the first structure, the control unit being furtherconfigured to control the plurality of drive devices so as to cause aforce generated by at least one of the plurality of drive devices to bereduced or zero when a predetermined timing is reached during the stopperiod.
 11. A control method of a wind turbine drive device, forcontrolling a drive device for moving two structures included in a windpower generation device relative to each other, the control methodcomprising: obtaining information related to a load occurring betweenthe drive device and one of the two structures that receives a forcegenerated by the drive device; and controlling the drive device so as tocause a force generated by the drive device to be reduced or zero basedon the information related to the load during a stop period in which thetwo structures are stopped relative to each other.
 12. A control methodof a wind turbine drive device, for controlling a drive device formoving two structures included in a wind power generation devicerelative to each other, the control method comprising: controlling thedrive device so as to cause a force generated by the drive device to bereduced or zero when a predetermined timing is reached during a stopperiod in which the two structures are stopped relative to each other.